Biomechanics: the study of the action of external and internal forces on the living body, especially on the skeletal system.

Location Terminology

Superior: referring to a point higher or above

Inferior: referring to a point lower or below

Proximal: referring to a point closer to the origin of a limb

Distal: referring to a point farther from the origin of a limb

Anterior (or ventral): referring to a point nearer to the front of the body

Posterior (or dorsal): referring to a point nearer to the back of the body

Medial: referring to a point nearer to the mid-line of the body

Lateral: referring to a point further from the mid-line of the body

Contralateral: referring to a point on the opposite side of the body

Ipsilateral: referring to a point on the same side of the body

Planes of Motion, Axes and Joint Motions

Anatomic position: the erect position of the body with the face and gaze directed anteriorly, the upper limbs at the side, and the palms of the hands directed anteriorly.

Sagittal plane: a longitudinal plane that divides the body of a bilaterally symmetrical animal into right and left sections.

Flexion: the act of bending a limb in the sagittal plane that typically decreases a joint angle.

Extension: the act of extending a limb that typically increases a joint angle.

Hyperextension: the extension of a part of the body beyond normal limits.

Frontal Plane: a vertical plane at right angles to a sagittal plane, dividing the body intoanterior and posterior portions. Also called frontal plane .

Abduction: the act of moving a limb in the frontal plane that typically moves the limb away from the mid-line of the body.

Adduction: the act of moving a limb in the frontal plane that typically moves the limb back toward the mid-line of the body.

Transverse Plane: a plane across the body at right angles to the coronal and sagittal plane and perpendicular to the longitudinal axis of a body or object; also, a plane dividing the body into an upper and lower section.

Internal Rotation: the act of rotating a limb in the transverse plane toward the mid-line of the body; or counter-clockwise when viewed from a superior view.

External Rotation: the act of rotating a limb in the transverse plane away from the mid-line of the body; or clockwise when viewed from a superior view.

Horizontal Abduction: transverse plane movement similar to that of a rear deltoid fly.

Horizontal Adduction: transverse plane movement similar to that of a chest fly.

Scapular Retraction: the act of sliding the shoulder blades toward the mid-line of the body.

Scapular Motion: the act of sliding the shoulder blades away from the mid-line of the body.

Scapular Depression: the act of sliding the shoulder blades inferiorly

Scapular Elevation: the act of sliding the shoulder blades superiorly

Muscle Actions

*Eccentric

Eccentric muscle action: when a muscle contraction is accompanied by lengthening muscle tissue.

*Concentric

Concentric muscle action: when a muscle contraction is accompanied by shortening muscle tissue.

*Isometric

Isometric muscle action: when a muscle contraction is accompanied by no change in the length of the muscle tissue.

*Isokinetic

Isokinetic muscle action: when a muscle maintains a constant speed during contraction.

Force: movement that results in the slowing down or speeding up of an object.

Torque: something that produces or tends to produce torsion or rotation; the moment of a force or system of forces tending to cause rotation.

Compare to – Three Planes of Motion

Compare to – Planes, Motions, and Axes

Frontal

Divides the body into anterior and posterior portions

Anterior-Posterior Axis

Abduction and Adduction

Plane

Joint Motion

Axis of Rotation

Exercise

Frontal

Adduction/Abduction

&

Ankle Eversion/ Inversion

&

Lateral Flexion

Anterior-Posterior

Abduction:

Barbell shoulder press Cable hip abduction

Adduction:

Pull up, Cable hip adduction

Transverse

Divides the body into top and bottom portions

Longitudinal or vertical axis

Movements include all rotation, pronation, supination, horizontal abduction and adduction.

Plane

Joint Motion

Axis of Rotation

Exercise

Transverse

Internal Rotation External Rotation

&

Horizontal Adduction Horizontal Abduction

&

Pronation Supination

Longitudinal

or

Vertical

Internal Rotation: Band Internal Rotation

Trunk Rotation: Wood chop

Horizontal Adduction: Cable Chest Fly

Horizontal Abduction: Rear delt fly machine

Sagittal

Divides the body into left and right halves

Coronal or medial-lateral axis

Flexion and extension

Plane

Joint Motion

Axis of Rotation

Exercise

Sagittal

Flexion

&

Extension

Medial-Lateral

A.K.A.

Coronal

Flexion:

Hamstring curl Barbell curl

Extension:

Quad Extension, Triceps Skull Crusher

Compare to Common force couples

Muscles

Movement Created

Shortening of the biceps brachii, brachioradialis, and brachialis

Elbow flexion in a Bicep Curl

Shortening of the Psoas major and minor, rectus femoris and illiacus

Hip Flexion in a leg lift

Shortening of the Pectoralis Major, Subscapularis and latissimus dorsi

Shoulder internal rotation

Different muscles pull from different angles but all work to produce the same joint movement. The biceps, brachioradialis and brachialis muscle all insert into different locations, but all work to flex the elbow.

Compare to Levers

There are three types of levers.

A first-class lever is a stick where the fulcrum is between the weight and the energy moving the weight (your hands, for example). Some common first-class levers are see-saws, crowbars, pliers, scissors (which use two first-class levers together), and a hammer pulling a nail.

A second-class lever is a stick where the fulcrum is at one end of the stick, you push on the other end, and the weight is in the middle of the stick. Some common second-class levers are doors, staplers, wheelbarrows, and can openers.

A third-class lever is a stick where the fulcrum is at one end of the stick, you push on the middle, and the weight is at the other end of the stick. With a third-class lever, you have to put in more energy than you would just lifting the weight, but you get the weight to move a longer distance in return. Some common examples are a broom, a hoe, a fishing rod, a baseball bat, and our own human arms.